Injection of a self-consistent beam at the spallation neutron source

We propose to demonstrate the injection of a self-consistent beam into the Spallation Neutron Source (SNS). Self-consistent beam distributions are defined to be ellipsoidal, or elliptical in 2D, distributions that have uniform density and that retain these properties under all linear transformations. Self-consistent distributions exhibit linear space charge forces and, because of their linear transport properties, may undergo very little halo formation if realized in practice. Some self-consistent distributions may also be manipulated to generate flat beams. Self-consistent distributions involve very special relationships between the phase space coordinates, making them singular in some respects and difficult to realize experimentally. The most famous self-consistent distribution is the K-V distribution, but now many other self-consistent distributions have been discovered. One such distribution, the 2D rotating distribution, can be painted as a coasting beam into the SNS accumulator ring, with slight modification of the lattice. Because the bunch length in the SNS ring is very long, it is expected that the coasting beam assumption will be a good approximation during accumulation. However, it is unknown how robust self-consistent distributions will be under real world transport in the presence of nonlinearities and other collective effects. This paper studies these issues and the mitigation of unwanted effects by applying realistic detailed computational models to the simulation of the injection of rotating beams into SNS. The result is a feasible prescription for the injection of a rotating self-consistent distribution into the SNS.